The ink used in inkjet printers typically comprises 20% by volume of pigment or dye with traces of various additives, some of which are volatile. The balance, i.e., substantially 80%, is water. When a swath of such ink is deposited on a print media, it requires a drying time before the next swath is printed to avoid bleeding problems between the swaths. An end of plot drying time is also required to avoid ink becoming smeared during transfer of the print media to the next stage.
To allow the ink to dry naturally takes a relatively long time, which has an adverse effect on throughput, so inkjet printers and other hardcopy apparatus which are in heavy use are provided with active drying systems, which eliminate moisture content from the printed surface as quickly as possible. Typically the active drying system comprises a fan and ducting system to flow air over the ink in the print zone, and/or a heater arranged under the printing platen to evaporate the moisture.
Since the vapor created by the drying system is predominantly water, the atmosphere in a room containing a hardcopy apparatus in heavy use can become unacceptably humid, with condensation forming on windows and walls. A large ink-jet printer can produce approximately 1 liter of water per hour.